#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{
    int a = 0;
    int i = 0;
    int sum = 0;
    while (i<5)
    {
        scanf("%d", &a);
        i++;
        sum += a;
    }
    printf("%.1lf\n", sum / 5.0);
    return 0;
}